Monoclonal antibodies have been developed against Coxsackie B4 and Encephalomyocarditis (EMC) viruses. These antibodies have been used to identify antigenic variations among these viruses. Attempts are underway to see whether there is a correlation between tissue tropism of these viruses and expression ofcertain antigenic determinants. Monoclonal autoantibodies against pituitary, stomach, intestine, pancreas, etc. have been obtained from splenic lymphocytes of reovirus type 1 infected mice. These autoantibodies will be used to examine the spectrum of autoimmune responses in polyendocrine disease. Hybridoma technology is also being used in an attempt to obtain stable cell lines capable of producing monoclonal hormones.